Bubble dynamics and deformation in microgravity

Abstract
Studies on two-phase flows have been perfomed at the Institut de Mécanique des Fluides de Toulouse for the past ten years, to improve the knowledge of the two-phase gas-liquid flows in normal and microgravity conditions, in order to optimize the design of the terrestrial and space thermohydraulic systems (evaporators, condensers, heat exchangers...). The preceding studies were mainly focused on bubble coalescence, break-up and dispersion in turbulent flows. The specific role of the turbulence has been isolated through microgravity experiments in which the bubble slip velocity vanishes. Interesting results were obtained highlighting a spectacular rate of coalescence in microgravity and also the role of the eigen dynamics of the bubbles in their deformation and rupture. We now propose to study the action of a mean velocity field on the various physical mechanisms that control the bubble size in a flow: their growth and detachment at a wall, their deformation and rupture and their coalescence. Experiments will be carried out in a Couette flow between 2 coaxial rotating cylinders, in a first step on ground with two neutrally buoyant liquids and in a second step in microgravity, with bubbles.